General G7C: Transmitter and receiver building blocks
These are the 14 official questions in group G7C of the 2023–2027 General question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- G7C01Question 1
What circuit is used to select one of the sidebands from a balanced modulator?
- ACarrier oscillator
- BFilter Correct
- CIF amplifier
- DRF amplifier
Why: A filter selects one sideband from a balanced modulator's output.
- G7C02Question 2
What output is produced by a balanced modulator?
- AFrequency modulated RF
- BAudio with equalized frequency response
- CAudio extracted from the modulation signal
- DDouble-sideband modulated RF Correct
Why: A balanced modulator produces double-sideband RF without the carrier.
- G7C03Question 3
What is one reason to use an impedance matching transformer at a transmitter output?
- ATo minimize transmitter power output
- BTo present the desired impedance to the transmitter and feed line Correct
- CTo reduce power supply ripple
- DTo minimize radiation resistance
Why: A matching transformer presents the right impedance to the transmitter and the feed line.
- G7C04Question 4
How is a product detector used?
- AUsed in test gear to detect spurious mixing products
- BUsed in a transmitter to perform frequency multiplication
- CUsed in an FM receiver to filter out unwanted sidebands
- DUsed in a single sideband receiver to extract the modulated signal Correct
Why: A product detector recovers the audio from an SSB signal.
- G7C05Question 5
Which of the following is characteristic of a direct digital synthesizer (DDS)?
- AExtremely narrow tuning range
- BRelatively high-power output
- CPure sine wave output
- DVariable output frequency with the stability of a crystal oscillator Correct
Why: A DDS gives a variable output frequency with crystal-oscillator stability.
- G7C06Question 6
Which of the following is an advantage of a digital signal processing (DSP) filter compared to an analog filter?
- AA wide range of filter bandwidths and shapes can be created Correct
- BFewer digital components are required
- CMixing products are greatly reduced
- DThe DSP filter is much more effective at VHF frequencies
Why: DSP can create a wide range of filter bandwidths and shapes.
- G7C07Question 7
What term specifies a filter’s attenuation inside its passband?
- AInsertion loss Correct
- BReturn loss
- CQ
- DUltimate rejection
Why: Insertion loss is a filter's attenuation inside its passband.
- G7C08Question 8
Which parameter affects receiver sensitivity?
- AInput amplifier gain
- BDemodulator stage bandwidth
- CInput amplifier noise figure
- DAll these choices are correct Correct
Why: Noise figure, bandwidth and input gain all affect sensitivity. All the choices are correct.
- G7C09Question 9
What is the phase difference between the I and Q RF signals that software-defined radio (SDR) equipment uses for modulation and demodulation?
- AZero
- B90 degrees Correct
- C180 degrees
- D45 degrees
Why: I and Q signals are 90 degrees apart.
- G7C10Question 10
What is an advantage of using I-Q modulation with software-defined radios (SDRs)?
- AThe need for high resolution analog-to-digital converters is eliminated
- BAll types of modulation can be created with appropriate processing Correct
- CMinimum detectible signal level is reduced
- DAutomatic conversion of the signal from digital to analog
Why: With I-Q and the right processing, an SDR can create any type of modulation.
- G7C11Question 11
Which of these functions is performed by software in a software-defined radio (SDR)?
- AFiltering
- BDetection
- CModulation
- DAll these choices are correct Correct
Why: An SDR does filtering, demodulation and decoding in software. All the choices are correct.
- G7C12Question 12
What is the frequency above which a low-pass filter’s output power is less than half the input power?
- ANotch frequency
- BNeper frequency
- CCutoff frequency Correct
- DRolloff frequency
Why: The cutoff frequency is where output drops below half the input power.
- G7C13Question 13
What term specifies a filter’s maximum ability to reject signals outside its passband?
- ANotch depth
- BRolloff
- CInsertion loss
- DUltimate rejection Correct
Why: Ultimate rejection is a filter's maximum attenuation outside its passband.
- G7C14Question 14
The bandwidth of a band-pass filter is measured between what two frequencies?
- AUpper and lower half-power Correct
- BCutoff and rolloff
- CPole and zero
- DImage and harmonic
Why: Band-pass bandwidth is measured between the upper and lower half-power points.